This project is designed to characterize in functional terms the antigen-sensitive cell populations in the intestine and to define the pathways by which intestinal antigen-sensitive cells can be induced by antigen to express humoral and cell-mediated effector functions. Differences in peripheral B cell populations have been examined using deficient fetal bovine serum. These studies suggest that murine Peyer's patches and lymph nodes contain an antigen-experienced B cell population while spleens contain predominantly antigen-inexperienced B cells. Peyer's patches have been examined for carrier priming of T cells after oral antigen administration. Studies to date indicate that Peyer's patch cells but not spleen cells can be carrier-primed for T cell helper function by feeding cellular antigens. Finally, studies have shown that spleen cells but not Peyer's patch cells can kill lipopolysaccharide- coated target cells by an antibody-dependent cell-mediated cytotoxic mechanism. Further studies are investigating the possible role of this mechanism of killing in immune tissue injury in certain intestinal diseases.